curiousity: 383 ci, intake ? and carb size

MYBAD79

MYBAD79

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While I am (for now) happy with the performance of my 383 SB I am curious how much "better" it would be with better matching components.

Up for discussion, here's my setup (the heads, intake and carb are leftovers from my 350) :

4 bolt main block, 383 stroker crank, forged pistons, 9.8:1 CR with Edelbrock RPM heads 170cc runners, 64cc chambers, thin head gasket (.028") and decked block... cam: comp 230-236, .510/.520 lift 112 LS, stock 1.5 rockers (roller tip)
Intake: Edelbrock Performer, Carb: Edelbrock 1405, 600cfm


I guess it's obvious that the intake and carb are not the best choice for a 383 with a relatively hot cam.

Questions:
- how much will I gain when I install a better intake and a 750cfm carb ???
- am I starving the engine or run it too lean with the small carb ???

Spark plugs look good.... engine runs an feels great..... again: the heads, intake and carb are leftovers from my 350.. if I had a bottomless wallet I'd dump them in a heartbeat for something better (Brodix. Dart, did I mention AFR?)
 
A dual plane intake will give you a better bottom end. They're pretty flat too. If you get a tall open plenum single plane, the bottom (low) end will be dead as a sack of hammers, but it'll wake up as soon as the cam starts getting into the lower end of it's designed power band. You'll also need to jet it a bit toward the rich side from where it is now. A carb that has a higher flow will help too. A 750 will probably be just a bit big for low and midranges, and not quite enough for big RPM power.
 
big_G said:
Go with a Performer RPM intake and a 750 cfm carb.
Click to expand...

The L88 hood will be fine for a RPM intake and I already have a Holley 750cfm carb on the shelf (old, needs a rebuild)

I am not going to spend the money on the swap any time soon - I have the steering rack conversion and the trailing arms to do first.... but I am curious what would I gain from the intake/carb swap ???

Am I hurting the engine with the current (small) carb ??? Too lean at higher RPM ??

How bad is my current combo from a pro's point of view ??? OK, I know it's not perfect... I had to re-use the heads because I didn't want to spend another $1200 at the time... just curious how much better/more powerful could the engine be with better heads/intake /carb ???
 
Hard to say how much you're leaving on the table, but everything in your combo is too small for a 383. A 383 likes 190-200 cc intake runners in the head, the cam is just a little small in duration, but matches the comp. ratio pretty good. The intake and carb. are more suited on a 327. The 600 cfm carb. won't make it leaner or richer, it will just be down on power. I'll bet you are down 75 hp easy.
 
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A friend over here has a 383 with 190 runners and an Edelbrock air gap intake and is running a Edelbrock 1405, 600cfm, the motor seams to run healthy as is. Maybe a 750 cfm carb will give him a little more at the higher RPMs but how often does anyone rev there motor that high on the street?
 
big_G said:
Hard to say how much you're leaving on the table, but everything in your combo is too small for a 383. A 383 likes 190-200 cc intake runners in the head, the cam is just a little small in duration, but matches the comp. ratio pretty good. The intake and carb. are more suited on a 327. The 600 cfm carb. won't make it leaner or richer, it will just be down on power. I'll bet you are down 75 hp easy.
Click to expand...

I agree with what he said. All seems like it can be a little bigger. Going from 1.5 to 1.6 rockers will make the cam seem to attack faster and wake the car up a little.
 
BangkokDean said:
A friend over here has a 383 with 190 runners and an Edelbrock air gap intake and is running a Edelbrock 1405, 600cfm, the motor seams to run healthy as is. Maybe a 750 cfm carb will give him a little more at the higher RPMs but how often does anyone rev there motor that high on the street?
Click to expand...

I'd do the carb last. IMO that is the least of the issues.
 
I am going to disagree slightly with you guys. I think that his heads are too small for his displacement and camshaft. Getting a different intake and or carb is only going to have minimal gains.

I wouldnt be looking at an RPM airgap, I would be sticking to the performer airgap and his 600cfm carb is fine. Maybe switch his cam for something smaller like 218/224 and maximize the low end torque.
 
I am running an Edelbrock Air Gap Intake with a Holley 750. Low 13's at the track, good manners on the street. I could probably get into the 12's with an aggressive tune up and drag radials, faster still if I switched to an automatic, but WTF, I like it like it is.

100_2619.jpg
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Hey, B2B, recognize the V/C's?

And before you guys tell me - I already got rid of the dangerous POS gas filter and got a solid metal one.
 
guru said:
I am going to disagree slightly with you guys. I think that his heads are too small for his displacement and camshaft. Getting a different intake and or carb is only going to have minimal gains.

I wouldnt be looking at an RPM airgap, I would be sticking to the performer airgap and his 600cfm carb is fine. Maybe switch his cam for something smaller like 218/224 and maximize the low end torque.
Click to expand...

I agree as this engine with the small runners and small cam and rockers your not going to consume enough air to make a 750 carb work.

You may see a bigger differance going to a HP 600 Holley over the Eldy carb.

Here are a couple of 383' we have dyned with 600 carbs
http://www.chevelles.com/forums/showthread.php?t=106715

Here is one we dyned with a 600 HP and a 2925 super victor.
http://www.chevelles.com/forums/showthread.php?t=106715
 
Thanks guys. Looks like the heads are the biggest problem... I sortof expected it .... eventually I'll need some better heads..... but as I said, for now the engine runs fine and I'm ok with the power - feels great :cool:

These Edelbrock heads are good for .575" lift so my first mod is going to be the 1.6 ratio rockers ... any other set of heads will be supporting more lift than the edelbrocks so the money for the rockers won't be wasted...

How terrible is this Performer intake that I have ? I "heard" it's barely better than the stock cast iron intake ???
 
If I recall correctly professional products intake makes more HP than an eldebrock

I have two of them myself and the castings are excellent, I don't even need to gasket match them
 
big_G said:
I've heard that the Performer is a lighter version of the stock cast iron manifold.
Click to expand...



Ok, so there's "some" improvement :lol:

The rockers are a quick and easy swap but I'm thinking the Performer intake will be limiting (or eliminate) the effect of 1.6 ratio rockers. I better do the intake and the rockers together.... then later worry about the heads.
 
MYBAD79 said:
big_G said:
I've heard that the Performer is a lighter version of the stock cast iron manifold.
Click to expand...



Ok, so there's "some" improvement :lol:

The rockers are a quick and easy swap but I'm thinking the Performer intake will be limiting (or eliminate) the effect of 1.6 ratio rockers. I better do the intake and the rockers together.... then later worry about the heads.
Click to expand...

FYI... I just finished a build using Edelbrock RPM heads and intake with a Holley Street Avenger carb. (670cfm) using a dropped base air cleaner. It fit under a small block stock hood.
 
Yellow73SB said:
If I recall correctly professional products intake makes more HP than an eldebrock

I have two of them myself and the castings are excellent, I don't even need to gasket match them
Click to expand...

who sells these ? I was looking at Jeg's catalog and they have the RPM manifold and a Weiland Stealth high rise - the advertized numbers look a lot better than the Performer intake....
 
MYBAD79 said:
Yellow73SB said:
If I recall correctly professional products intake makes more HP than an eldebrock

I have two of them myself and the castings are excellent, I don't even need to gasket match them
Click to expand...

who sells these ? I was looking at Jeg's catalog and they have the RPM manifold and a Weiland Stealth high rise - the advertized numbers look a lot better than the Performer intake....
Click to expand...

Karsten, I was talking with Dick Murray a few days ago and he said he will match Jeg's prices. BTW...I was looking at their intake manifolds today and they had an Air-Gap hanging on the wall. This was their Palm Bay store. Check them out with a look see.
 
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